Heretofore, a pressure sensor has been known, which detects a pressure by detecting a quantity of displacement caused in a diaphragm section when the diaphragm section receives the pressure. In order to enhance sensitivity of the pressure sensor as described above without changing a constituent material thereof, it is necessary to increase a pressure receiving area of the diaphragm section or such a displacement quantity per unit pressure. However, in recent years, device miniaturization has been strongly required, and accordingly, it is difficult to enhance the sensitivity of the pressure sensor by increasing the pressure receiving area of the diaphragm section. From such a background, it is desired to enhance the sensitivity of the pressure sensor by increasing the displacement quantity of the diaphragm section per unit pressure.
As shown in the following Expression (1), a displacement quantity y at a center of a disc-like diaphragm section is determined based on properties of a material that composes the diaphragm section, and on a size (area) and thickness of the diaphragm section. Note that, in Expression (1), parameters ν, E, t, a and P indicate a Poisson's ratio and Young's modulus of the material that composes the diaphragm section, the thickness and radius of the diaphragm section, and the pressure applied to the diaphragm section, respectively. Specifically, the thickness t of the diaphragm section is thinned, whereby the displacement quantity y of the diaphragm section per unit pressure is increased, and the sensitivity of the pressure sensor can be enhanced. However, in the case where the thickness t of the diaphragm section is thinned, when an excessive pressure is applied to the diaphragm section, there is a possibility that the diaphragm section may be broken since the diaphragm section cannot resist the pressure concerned. From such a background, it is desired to provide a high-sensitivity and small-size pressure sensor having high pressure resistance, that is, the pressure sensor less likely to be broken even in the case where the excessive pressure is applied thereto.y=( 3/16)×{(1−ν2)/Et3}×a4p   (1)
The present invention has been made in order to solve the foregoing problem. It is an object of the present invention to provide the high-sensitivity and small-size pressure sensor that is less likely to be broken even in the case where the excessive pressure is applied thereto.